A few venture capitalists in Silicon Valley think there's nothing wrong with what Facebook did. Chris Dixon, a partner at Andreessen Horowitz, says if companies can A/B test to make more money, why can't they A/B test to "advance science?"

If you a/b test to make more money that's fine, but if you a/b test to advance science that's bad? I don't get it.

Marc Andreessen, the firm's co-founder and a Facebook board member, agrees with Dixon. He likens Facebook's experiment to "literally any movie where anything bad happens." Movies, Andreessen explains, also try to make you feel things. And, he points out, if you don't like Facebook's tactics you can get off the social network altogether.

Here are the rest of Andreessen's Twitter posts defending Facebook's decision to turn 700,000 people into subjects of an experiment. "A year ago, Facebook was accused of making you feel unhappy by showing you too many happy things," Andreessen says. "Faced with that question, what would you do? Show more sad things? Show more happy things? Or study the topic?"